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United States Patent |
5,077,855
|
Ambasz
|
January 7, 1992
|
Motor-driven toothbrush
Abstract
A motor-driven toothbrush comprises a drive unit having a motor and a
transmission that simultaneously drive a shaft in rotation and a brush
head extension reciprocably in a direction parallel to the axis of the
shaft. A brush unit includes a brush head coupled to the extension for
lengthwise reciprocating motion on which several bristle holders, each
carrying several bristle tufts, are mounted individually for pivotal
movement about an axis spaced apart from and parallel to the drive shaft.
A crank coupled to the drive shaft imparts pivotal movement to each
bristle holder individually via a crank pin for each holder.
Inventors:
|
Ambasz; Emilio (295 Central Park West, New York, NY 10024)
|
Appl. No.:
|
533524 |
Filed:
|
June 5, 1990 |
Current U.S. Class: |
15/22.1; 15/22.2; 74/22R |
Intern'l Class: |
A46B 013/02; A46B 007/06 |
Field of Search: |
15/22.1,22.2
74/22 R,70
132/271,221,313
|
References Cited
U.S. Patent Documents
1517320 | Dec., 1924 | Stoddart | 15/22.
|
2184850 | Dec., 1939 | Schloss | 15/22.
|
2196667 | Apr., 1940 | Moseley | 15/22.
|
2278365 | Mar., 1942 | Daniels | 15/22.
|
3562566 | Feb., 1971 | Kircher | 15/22.
|
3935869 | Feb., 1976 | Reinsch | 15/22.
|
4545087 | Oct., 1985 | Nahum | 15/22.
|
Foreign Patent Documents |
357863 | Mar., 1990 | EP | 15/22.
|
3544256 | Jun., 1987 | DE | 15/22.
|
Primary Examiner: Coe; Philip R.
Assistant Examiner: Till; Terrence R.
Attorney, Agent or Firm: Brumbaugh, Graves, Donohue & Raymond
Claims
I claim:
1. A motor-driven toothbrush having a drive unit that includes a motor and
a transmission driven by the motor received in a hand-holdable casing; a
brush unit that includes an elongated brush head arranged to be coupled at
one end to the drive unit and a multiplicity of bristle holders movably
mounted adjacent the other end of the brush head, each bristle holder
having bristles affixed to it; and a drive shaft coupling the transmission
to the bristle holders to impart movement to them relative to the brush
head; characterized in that the transmission includes an output drive gear
rotatable about an axis substantially coincident with the axis of the
brush head, the drive shaft is coupled to the output drive gear so as to
be driven in rotation thereby, the bristle holders are pivotably mounted
individually on the brush head for rotation about a common mounting axis
parallel to and spaced apart from the drive shaft axis, and each bristle
holder is coupled to the drive shaft by crank means for imparting
oscillatory pivotal motion to each holder individually about the mounting
axis.
2. A motor-driven toothbrush according to claim 1 and further characterized
in that each of the bristle holders has a mounting hole, and a mounting
pin is affixed to the brush head and is received through the holes in the
bristle holders.
3. A motor-driven toothbrush according to claim 2 and further characterized
in that the crank means includes a crankshaft having a crank pin for each
bristle holder and a crank pin follower portion on each bristle holder
spaced apart from the mounting axis and receiving a corresponding crank
pin.
4. A motor-driven toothbrush according to claim 3 and further characterized
in that the crank pins for some of the bristle holders are
circumferentially spaced apart from the crank pins for others of the
bristle holders.
5. A motor-driven toothbrush according to claim 4 and further characterized
in that axially adjacent crank pins are circumferentially spaced apart by
180.degree. of arc such that the oscillations of adjacent brush holders
are 180.degree. out of phase.
6. A motor-driven toothbrush according to claim 4 and further characterized
in that adjacent pairs of crank pins are connected by crank arms having
shoulders that engage surfaces of adjacent bristle holders such as to
retain the bristle holders in axially closely-spaced positions on the
crankshaft.
7. A motor-driven toothbrush according to claim 6 and further characterized
in that the surfaces of the bristle holders engaged by the crank arms are
recesses in opposite side walls of the bristle holders.
8. A motor-driven toothbrush according to claim 3 and further characterized
in that the crank pin follower portion of each bristle holder is a notch
opening in an edge of the holder opposite from an edge from which the
bristles protrude.
9. A motor-driven toothbrush according to claim 1 and further characterized
in that the brush head has adjacent its end remote from the drive unit a
cavity forming an opening in a side wall, the bristle holders are
identical plate-like members received side by side in closely spaced
relation in the cavity, each bristle holder carries along an edge facing
outwardly from the cavity a row of several bristle tufts, a mounting pin
extends lengthwise of the brush head across the cavity opening and is
fastened to the brush head, each bristle holder has a hole pivotably
receiving the mounting pin, a crankshaft extends lengthwise of the brush
head into the cavity on the opposite side of the mounting pin from the
cavity opening, and a crank pin on the crankshaft engages crank pin
follower surfaces on each bristle holder.
10. A motor-driven toothbrush according to claim 9 and further
characterized in that the edges of the bristle holders from which the
bristle tufts extend are substantially contiguous to an imaginary surface
bounded by the edge of the cavity opening.
11. A motor-driven toothbrush according to claim 1 and further
characterized in that the brush unit is detachably coupled to the drive
unit.
12. A motor-driven toothbrush according to claim 11 and further
characterized in that the crank means includes a crankshaft rotatably
received in the brush head and coupled to the bristle holders and there
are detachable coupling means on the drive shaft and the crankshaft for
joining them together axially and rotationally.
13. A motor-driven toothbrush according to claim 11 and further
characterized in that the drive unit includes a brush head extension
having a portion protruding from the casing and a portion of the brush
head is received in the end of the protruding portion in telescoping
relation.
14. A motor-driven toothbrush according to claim 1 and further
characterized in that the transmission includes an output member movable
in a direction lengthwise of the drive shaft and the brush head is coupled
to the output member such that it is driven lengthwise back and forth
relative to the drive unit simultaneously with the side-to-side
oscillations of the bristle holders relative to the drive unit.
15. A motor-driven toothbrush according to claim 14 and further
characterized in that at least a portion of the drive shaft that is
coupled to the bristle holders is movable longitudinally with the brush
head relative to the output drive gear of the transmission.
16. A motor-driven toothbrush according to claim 15 and further
characterized in that the output member is a member that is supported in
the casing of the drive unit for reciprocating linear motion parallel to
the axis of the drive shaft and has spaced-apart parallel cam follower
surfaces disposed perpendicularly to the axis of the drive shaft and the
transmission includes a cam rotatable about an axis perpendicular to the
drive shaft axis and parallel to the cam follower surfaces and having a
cam surface disposed eccentrically to its axis of rotation and engaging
the cam follower surfaces.
17. A motor-driven toothbrush according to claim 16 and further
characterized in that the cam consists of an inner part having a circular
cylindrical outer surface eccentric to its axis of rotation and an outer
part received for rotation through a predetermined arc about the outer
surface of the inner part, the cam surface being on the outer part and
being eccentric to the outer surface of the inner part, whereby when the
cam is driven in rotation in one direction the stroke of the output member
is different from its stroke when the cam is driven in the opposite
direction.
18. A motor-driven toothbrush according to claim 17 and further
characterized in that the motor is electrically connected to a power
source through a switch operable to reverse the driving direction of the
motor.
19. A motor-driven toothbrush according to claim 16 and further
characterized in that the cam is a portion of a crown gear and the output
drive gear and the crown gear are driven by a single pinion gear.
20. A motor-driven toothbrush according to claim 19 and further
characterized in that the motor has a motor gear affixed to its shaft, and
the pinion gear is coupled to the motor gear by a speed reduction gear
train.
21. A motor-driven toothbrush according to claim 20 and further
characterized in that the speed reduction gear train is a planetary gear
train having planet gears carried on shafts on a rotatable planetary gear
carrier and meshing with the motor gear and with a stationary ring gear,
and the pinion gear is affixed to the planetary gear carrier.
22. A motor-driven toothbrush according to claim 15 and further
characterized in that the output member is a brush head extension having a
portion protruding from the casing of the drive unit, and the brush unit
is detachably coupled to the brush head extension.
23. A motor-driven toothbrush according to claim 22 and further
characterized in that the casing has an end cap having an opening defined
by a guide flange that slidably supports the brush head extension for
reciprocating lengthwise motion.
24. A motor-driven toothbrush according to claim 22 and further
characterized in that the drive shaft is coupled to an output drive gear
of the transmission for rotation therewith and for axial motion with the
brush head extension relative to the output drive gear, and a crankshaft
is detachably coupled to the drive shaft for rotation and axial movement
therewith.
Description
FIELD OF THE INVENTION
The present invention relates to a motor-driven toothbrush and, in
particular, a motor-driven toothbrush in which the bristles and, at the
option of the user, the brush head carrying the bristles are moved
relative to a hand-holdable drive unit.
BACKGROUND OF THE INVENTION
Motor-driven toothbrushes have been proposed and marketed commercially for
many years, especially since long-lived rechargeable batteries and
miniature electric motors have been available. A common form of
motor-driven toothbrush comprises a hand-holdable drive unit and a brush
unit that is pivoted about its axis relative to the drive unit by a
motor-driven transmission, and thereby pivots the brushes as a unit from
side-to-side so that they brush generally up and down on the teeth. In
another known form a brush unit is reciprocated axially by a drive unit
such that the brush moves generally from side to side across the teeth. A
motor-driven toothbrush that allows the user to switch between a
side-to-side pivot motion and an axial reciprocating motion of the brush
head is currently being marketed. Also available is a motor-driven
toothbrush in which a single, relatively large tuft of bristles is rotated
unidirectionally about an axis parallel to the bristles in a manner
similar to that of a cleaning brush used in a dentist's drill head by
dental hygienists in cleaning teeth.
The motor driven toothbrush described and shown in U.S. Pat. No. 4,156,620
(Clemens, May 29, 1979) has a brush head carrying several bristle tufts,
each of which is mounted to rotate about its lengthwise axis on a tiny
spindle having a pinion gear. The bristle tufts are arranged in two ranks,
one on each side of the longitudinal axis of the brush head, and the gears
of the spindles of each rank mesh to form a train. Every other spindle in
each rank is offset laterally from the remaining spindles. A motor in a
hand-holdable drive unit drives through a gear transmission a crank arm
that is linked to a longitudinally movable drive shaft extending through
the brush head and having a rack gear on its end portion that meshes with
the pinion gears on alternate ones of the bristle-mounting spindles in
each rank. As the drive shaft reciprocates, the driven bristle tufts are
rotated, first in one direction and then the other. The remaining bristle
tufts are rotated in opposite directions to the driven ones due to the
intermeshing of the gears in each rank. A motor-driven toothbrush of the
type described and shown in the Clemens patent is widely sold.
Previously known motor-driven toothbrushes of the type in which the entire
brush unit is moved relative to the drive unit in either rotational or
axial reciprocation have several disadvantages. The bristle tufts, which
are arranged in crosswise and lengthwise rows, move along straight tracks
either up and down or crosswise over the teeth with gaps between the
tracks. Therefore, thorough cleaning requires that the user move the
device over the teeth to cover all areas, lest areas of the teeth not be
cleaned where the gaps between the tuft rows are. The reactive forces to
the brush movements are transmitted to the drive unit and by the brush
unit to the user's hand, and some people do not like the vibration felt by
the hand. Similarly, the back of the brush head often contacts and
vibrates the lips and the tissues in the mouth, which can also be
unpleasant for some users. The longitudinally reciprocating types of
brushes move exclusively across the teeth, and the bristles tend to move
past the spaces between the teeth. Massaging of the gums is important to
good dental hygiene, but the solely linear movements of the bristles do
not produce a thorough massaging action for stimulation of blood
circulation and tissue toning.
As far as cleaning the teeth is concerned, the individual rotating tufts of
the Clemens patent type toothbrush do an excellent job. Because the
individual tufts move very little transversely relative to their axes,
however, the gum-massaging action is limited. The single rotating bristle
tuft toothbrush requires considerable attention by the user to full
coverage of the teeth and also fails to massage the gum tissues
effectively.
SUMMARY OF THE INVENTION
One object of the present invention is to provide a motor-driven toothbrush
that not only cleans the teeth extremely well but massages the gums in a
unique and highly effective way. Another object is to reduce the vibration
of the drive unit due to reactive forces imposed on it by the brush unit.
Still another object is to provide two modes of brush action that can be
chosen by the user to suit best his or her brushing preference.
Advantageously, the user may brush with one mode and then go over the
teeth again in the other mode. In one mode, the back of the brush head is
not moved by the drive, which eliminates the vibrating contact with the
lips and the tissues of the mouth.
Like the previously-known motor-driven toothbrush of the Clemens patent
mentioned above, the toothbrush of the present invention has a drive unit
that includes a motor and a transmission driven by the motor, the motor
and transmission being received in a hand-holdable casing, and a brush
unit that includes an elongated brush head arranged to be coupled at one
end to the drive unit and a multiplicity of bristle holders movably
mounted adjacent the other end of the brush head, each bristle holder
having bristles affixed to it. A drive shaft couples the transmission to
the bristle holders to impart movement to them relative to the brush head.
The present invention is characterized in that the transmission includes an
output drive gear rotatable about an axis substantially coincident with
the axis of the brush head, the drive shaft is coupled to the output drive
gear so as to be driven in rotation thereby, the bristle holders are
pivotably mounted individually on the brush head for rotation about a
common mounting axis parallel to and spaced apart from the drive shaft
axis, and each bristle holder is coupled to the drive shaft by a crank pin
so that oscillatory pivotal motion is imparted separately to each holder
about the mounting axis.
In preferred embodiments of the invention each of the bristle holders has a
mounting hole, and a mounting pin is affixed to the brush head and is
received through the holes in the bristle holders. A crankshaft coupled to
the drive shaft has a crank pin for each bristle holder, and a crank pin
follower portion on each bristle holder spaced apart from the mounting
axis receives a corresponding crank pin. The crank pins for some of the
bristle holders are circumferentially spaced apart from the crank pins for
others of the bristle holders. For example, axially adjacent crank pins on
the crankshaft may be circumferentially spaced apart by 180.degree. of arc
such that the oscillations of adjacent brush holders are 180.degree. out
of phase. Adjacent pairs of crank pins on the crankshaft are connected by
crank arms having shoulders that engage surfaces of adjacent bristle
holders such as to retain the bristle holders in axially closely-spaced
positions on the crankshaft, the surfaces of the bristle holders engaged
by the crank arms preferably being recesses in opposite side walls of the
bristle holders. Advantageously, the crank pin follower portion of each
bristle holder is a notch opening in an edge of the holder opposite from
an edge from which the bristles extend, which facilitates assembly of the
brush unit.
The brush head has at the brush end a cavity forming an opening in a side
wall. The bristle holders are identical plate-like members received side
by side in closely spaced relation in the cavity, each bristle holder
carrying along an edge facing outwardly from the cavity a row of several
bristle tufts. The mounting pin extends lengthwise of the brush head
across the cavity opening and is fastened to the brush head. The
crankshaft extends lengthwise of the brush head into the cavity on the
opposite side of the mounting pin from the cavity opening. The edges of
the bristle holder from which the bristle tufts extend are substantially
contiguous to an imaginary surface bounded by the edge of the cavity
opening.
In preferred embodiments, furthermore, the brush unit is detachably coupled
to the drive unit so that the drive unit can be used interchangeably with
numerous brush units. The crankshaft is arranged to be detachably coupled
to the drive shaft axially and rotationally. The drive unit includes a
brush head extension having a portion protruding from the casing, and a
socket portion of the brush head is received on the end of the protruding
portion in telescoping relation.
As an optional but highly desirable further characteristic of the
invention, the transmission includes an output member movable back and
forth in a direction lengthwise of the drive shaft, and the brush head is
coupled to the output member such that it is driven lengthwise back and
forth relative to the drive unit simultaneously with the side-to-side
oscillation of the bristle holders relative to the drive unit. The output
member is a member supported in the casing of the drive unit for
reciprocating linear motion parallel to the axis of the drive shaft and
having spaced-apart parallel cam follower surfaces disposed
perpendicularly to the axis of the drive shaft, and the transmission
includes a cam rotatable about an axis perpendicular to the drive shaft
axis and parallel to the cam follower surfaces and having a cam surface
that is eccentric to its axis of rotation and engages the cam follower
surfaces. In particular, the output member may be a brush head extension
having a portion protruding from the casing of the drive unit, and the
brush unit is arranged to be detachably coupled to the brush head
extension. The casing has an end cap having an opening defined by a guide
flange that slidably supports the brush head extension for reciprocating
motion. The drive shaft is coupled to the output drive gear of the
transmission for rotation therewith and axial motion with the brush head
extension relative thereto. The crankshaft of the brush unit is detachably
coupled to the drive shaft.
Optionally, though preferably, the cam consists of an inner part having a
circular cylindrical outer surface eccentric to its axis of rotation and
an outer part received for rotation through a predetermined arc about the
outer surface of the inner part, the cam surface being on the outer part
and being eccentric to the outer surface of the inner part. When the cam
is driven in rotation in one direction, the stroke of the output member is
different from its stroke when the cam is driven in the opposite
direction. The motor and battery are electrically connected through a
switch operable to reverse the driving direction of the motor.
The cam that drives the brush head extension may be a portion of a crown
gear, and the output drive gear and the crown gear are driven by a single
pinion gear. The motor has a motor gear affixed to its shaft, and the
pinion gear is coupled to the motor gear by a speed reduction gear train,
for example, a planetary gear train having planet gears carried on shafts
on a rotatable planetary gear carrier and meshing with the motor gear and
with a stationary ring gear. The pinion gear is affixed to the planetary
gear carrier.
A motor driven toothbrush according to the present invention is used by
holding it with the brush head oriented generally crosswise of the teeth
so that the laterally oscillating bristle tufts move generally vertically
on the teeth. When operated in the combined-motion mode, in which the
brush head reciprocates lengthwise as the bristle tufts oscillate
laterally, the front and back surfaces of the teeth are cleaned very
effectively by the combined crosswise and vertical movements of the
bristles. In a preferred design, the frequency of the lateral oscillation
is at least about twice the frequency of the lengthwise reciprocation,
which causes the bristle tufts to move in a sideways figure "8" pattern.
Also preferably, adjacent bristle holders oscillate laterally 180.degree.
out of phase, so that the directions of the figure "8" patterns of the
tufts of adjacent holders are opposite. It is believed that the
out-of-phase figure "8" patterns are very effective in massaging the gums
by working the tissues on a relatively fine scale omni-directionally.
The lengthwise motion of the brush head ensures good lateral coverage of
the teeth, while the lateral motions of the bristle tufts dislodge debris
and plaque by working vertically, the cleaning effect being especially
desirable at the gum line due to the vertical components of the tuft
movements that work the bristles perpendicularly against the gum line
area. Cleaning at the gumline appears to be enhanced by the out-of-phase
lateral oscillations of the bristle tufts; while the tufts of alternate
holders push the gum up, thereby exposing the teeth at the gumline, the
tufts of the remaining holders move down and remove plaque and debris. The
crosswise (relative to the teeth) components of the tuft movements aid in
working the bristles against the gumline by sliding them along the gumline
simultaneously with moving them toward or away from the gumline. It is
these same complex, simultaneous omni-directional motions that promote
blood circulation by pushing and pulling the gum tissue in many directions
between adjacent tufts that are moving in opposite directions, in all
directions and out of phase.
Following brushing in the combined-motion mode, it is desirable to go over
the teeth again with the toothbrush operated in the single-motion mode
(lateral tuft movements only), which will cleanse the spaces between the
teeth by working the tufts solely vertically for better penetration
between the teeth.
When the motor-driven toothbrush of the present invention is operated
without lengthwise reciprocation of the brush unit, the brush head is not
moved by the drive unit and does not vibrate the lips or mouth tissues
when it touches them. With 180.degree. out-of-phase timing of the bristle
holders, the reaction forces of lateral movements of the bristle tufts
against the teeth are balanced, and no reaction forces are transmitted to
the drive unit, which, therefore, is not subject to vibration.
For a better understanding of the invention, reference may be made to the
following description of an exemplary embodiment and to the accompanying
drawings of the embodiment.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side cross-sectional view of the drive unit of the embodiment;
FIG. 2 is a front view of the drive unit with the casing broken away;
FIG. 3 is a top plan view of the drive unit;
FIG. 4 is a side cross-sectional view of the brush unit of the embodiment;
FIG. 5 is a front cross-sectional view of the brush head;
FIG. 6 is a front view of the brush end of the brush head;
FIG. 7 is a side elevational view of the brush end of the brush head;
FIG. 8 is an end elevational view of the brush end of the brush head;
FIG. 9 is an end cross-sectional view of the brush head taken along the
lines 9--9 of FIG. 7;
FIGS. 10 and 11 are end cross-sectional views of the brush unit crankshaft
taken through longitudinally adjacent crank pins;
FIG. 12 is an end view of the coupling end of the crankshaft;
FIGS. 13 and 14 are side and top cross-sectional views of the coupling end
of the crankshaft taken along the lines 13--13 and 14--14 of FIG. 12;
FIGS. 15 to 17 are a front view, a side view and a bottom view,
respectively, of a bristle holder of the brush head;
FIG. 18 is a side cross-sectional view of the brush holder taken along the
lines 18--18 of FIG. 16;
FIGS. 19 and 20 are plan views of the crown gear and the cam insert showing
the two rotational positions of the cam insert relative to the crown gear,
depending upon the direction of rotation of the crown gear;
FIG. 21 is a detail side cross-sectional view of the transmission and the
control switch on a larger scale than that of FIG. 1; and
FIG. 22 is a diagram of the electrical circuit of the drive unit.
DESCRIPTION OF THE EMBODIMENT
The drive unit 30 (FIGS. 1 to 3 and 21) comprises a miniature D.C. electric
motor 32 that is powered by two rechargeable batteries 34, 36 and drives a
transmission 38 through a motor gear 40 affixed to the motor shaft 42. The
batteries, motor and transmission are housed within a casing 44 having an
integral end wall 46 at the bottom end and an opening 48 at the other end
that receives a cap 50, which is sealed to the casing by a sealing ring
51.
The batteries 34, 36 are received in a generally tubular battery holder 52.
An end wall 54 of the holder 52 has two screw bosses 56 that receive
screws 58 inserted through the end wall 46 of the casing 44 for securing
the battery holder to the casing. Two electrical contact pins 60 are
received in bosses 62 on the battery holder and protrude through the
casing end wall 46. The contact pins mate with a receptacle in a
charger/holder (not shown) for the drive unit. The drive unit is stored
upright in the charger/holder when not in use, and while so stored, the
batteries are recharged. The positive terminal of the battery 34 is
soldered to an electrical lead 63 (a bent metal band, FIG. 2) having a
hole that receives one of the pins 60. Another metal band lead 64 connects
the negative terminal of the battery 36 to the other pin 60. The batteries
34, 36 are, of course, in end-to-end electrical contact in series. A diode
234 (see FIG. 22), which is physically located at the negative end of the
battery 36 nearest the motor 32, is interposed in the electrical circuit
between the negative terminal of the battery 36 and the negative contact
pin 60 for the charger/holder. The contact pins 60 and the screws 58 are
individually sealed to the casing end wall 46 by sealing rings 68 and 70
to prevent water from entering the casing.
The motor 32 is received in a cage-like motor holder 72 that includes a
transverse end wall portion 74 at the shaft end, an annular flange portion
76 extending from the wall portion 74 in a direction away from the motor
and lengthwise strips (not shown) that extend lengthwise along
diametrically opposite flat portions of the side walls of the motor case.
A cross piece 78 is joined to the ends of the strips, such as by
heat-staking lugs on the strips received through holes in the cross piece
78. Flanges 80 on the cross piece engage the end of the battery 36,
thereby to serve as a spacer between the battery and the motor. The motor
holder 72 is joined to the battery holder 52 by three circumferentially
spaced-apart hook portions 82 that extend from the flange portion 76 along
the sides of the motor 32 and snap into holes 84 in the battery holder 52.
Rotational positioning and restraint of the motor are enhanced by bosses
86 that extend into screw holes in the motor casing. Three elastomeric
foam pads (not shown), approximately equally spaced apart
circumferentially, are interposed between the flange portion 76 of the
motor holder 72 and the wall of the casing 44 to provide vibration and
noise isolation of the motor and transmission from the casing.
Each of three circumferentially spaced-apart planetary gears 88 (only one
is shown in FIGS. 1 and 21 and only one is required) is received on a
corresponding shaft 90 of a planetary gear carrier 92 that is received
with a rotationally sliding fit between the distal end of the flange
portion 76 of the motor holder and a shoulder 93 on a two-part gear
housing 94. The planetary gears 88 are elements of a planetary gear train
in which the motor gear 40 is the sun gear and the ring gear 96 is formed
on the inner surface of the flange portion 76 of the motor casing. The sun
gear (motor gear 40) drives the planetary gears 88, which react against
the stationary ring gear 96 and thereby orbit about the sun gear and
impart rotation to the planetary gear carrier 92 at a rotational speed (in
rpm) substantially less than that of the motor shaft.
A pinion gear portion 98 of the carrier 92 meshes with and drives a drive
gear 100 that is affixed to a drive shaft coupling 102. The drive shaft
coupling 102 is rotatably received in a sleeve 104 in a lower part 106 of
the gear housing 94 and is held axially in the sleeve by the face of the
gear 100 at one end and a flange portion 108 at the other end. An axial
hole 110 of square or other non-round cross-sectional shape in the drive
shaft coupling 102 receives with a sliding fit a correspondingly shaped
end portion 112 of a drive shaft 114.
A shaft 116, the axis of which intersects the axis of the motor shaft and
the gear 98 at a right angle, is mounted for rotation in an upper
receiving socket 118 in an upper part 120 of the gear housing 94 and a
lower receiving socket 121 in the lower gear housing part 106. A crown
gear 122 press fitted on the shaft 116 is held in mesh with the pinion
gear 98 of the planetary gear carrier by being captured axially of the
shaft 116 between wall portions 124 and 126 of the gear housing 94. An
integral eccentric drum cam boss 128 on the crown gear receives an
eccentric drum cam insert 130. The cam insert 130 and crown gear 122 have
abutments 132 and 134 that engage and restrict rotation of the cam insert
to 180.degree. relative to the cam boss. When the crown gear is driven in
one direction by the pinion gear 98, the external cam surface of the cam
insert is eccentric to the crown gear shaft 116 (see FIGS. 2 and 20), and
when it is driven in the other direction (FIG. 19), the cam surface of the
insert is concentric to the shaft 116.
The cam insert 130 works against the transversely extending, parallel walls
136 of a cam slot 138 in a brush head extension 140 that is slidably
supported for movement along the axis of the drive shaft 114 within a
guide flange portion 142 of the casing cap 50, with additional guiding
support being contributed by slideways on the lower gear housing part 106
and the extension that restrict up and down motions of the cam slot. When
the cam insert 128 is in its eccentric position relative to the crown gear
122, i.e., when the motor 32 drives the gear train formed by the planetary
gear train, the gear 98 and the crown gear in one direction, the brush
head extension is reciprocated axially relative to the casing. When the
gear train is driven in the opposite direction such as to cause the cam
insert 128 to stop in a position relative to the crown gear 122 in which
its cam surface is concentric to the crown gear, the brush head extension
140 remains stationary relative to the drive unit 30.
The drive shaft 114 is rotatably received in a hole 144 extending
lengthwise all the way through the brush head extension 140 and is fixed
axially to the extension by a retainer bushing 146 that is heat-staked in
place in a recess in the extension and engages a flange 148 on the drive
shaft. An O-ring 150 seals the annulus between the drive shaft 114 and the
extension 140. A flexible bellows seal 152 is attached by a flange 164 at
one end to the extension 140 and clamped by a split band clamp 156 at its
other end to the guide flange 142.
A brush unit 160, which is shown in FIG. 4, is detachably coupled to the
brush head extension 140 of the drive unit 30 so that a brush head for
each member of a household can be interchanged and used with a single
drive unit. A brush head 162 telescopically fits snugly by means of a
socket portion 164 at one end onto the external end of the extension. A
crankshaft 166 extends through a lengthwise hole 168 in the brush head and
is coupled by a bifurcated coupling portion 170 (see FIGS. 12 to 14) to
the external end of the drive shaft 114 of the drive unit. The drive
shaft, which is metal for durability, has a groove 172 (see FIG. 1) that
receives ribs 174 on the coupling portion 170 of the crankshaft. The tip
of the drive shaft has diametrically opposite flat surfaces and fits into
a socket portion 176 of the crankshaft that is of a corresponding
cross-sectional shape (see FIG. 12), so that the drive shaft and
crankshaft are rotationally fixed relative to each other.
Several identical bristle holders 178 (FIGS. 15 to 18)--six in the
embodiment--are received in a cavity 180 in the head end of the brush
head. Each holder 178 is a thin plate-like member having holes 180 along
its outwardly facing edge that receive tufts 181 of bristles. A transverse
hole 182 through each holder pivotably receives a mounting pin 184 (see
FIG. 4), one end of which is captured in a hole 186 at one end of the
cavity 180 of the brush head and the other end of which drops into a notch
188 formed by two tiny bosses 190 at the other end of the cavity. A pin
retainer cap 192 snaps onto the brush head by means of hooks on the cap
received in an opening 194 in the head. One of the hooks on the cap also
captures the pin 184 lengthwise. The pin 184 defines a pivot axis for the
bristle holders that is parallel to and spaced apart from the axis of the
crankshaft 166.
The crankshaft 166 has for each bristle holder 178 a crank pin 196 that is
received in a follower portion 198 of the corresponding holder in the form
of a notch having side walls parallel to each other and to a plane defined
by the axis of the crankshaft 166 and the axis of the mounting pin 184.
Each pin 196 is, of course, eccentric to the axis of the crankshaft and is
joined to a crank arm 199 (see FIGS. 10 and 11). Preferably, but not
indispensably, alternate crank pins are aligned on one side of the shaft
axis while the remaining crank pins are aligned on the diametrically
opposite side of the shaft axis. Upon rotation of the crankshaft adjacent
bristle holders are pivoted about the pivot axis--the pin 184--from side
to side in opposite directions, 180.degree. out of phase, with this
arrangement of the crank pins. The faces of the crank arms 199 adjacent
the crank pins engage the faces of recesses 200 and hold the bristle
holders 178 in closely adjacent positions in the cavity for proper
tracking of the crank pins and for stabilizing the bristle holders against
longitudinal cocking. A round boss 202 on the end of the crankshaft is
received in a hole 204 in the end wall of the recess 180 of the brush head
162 to support as a bearing the crankshaft on its rotational axis
transversely.
The motor 32 is turned on and off, and its direction of rotation is
controlled, by a switch assembly 210 installed on the cap 50 (FIGS. 1 and
21). A printed circuit board 212 having contacts connected by wires to the
motor and battery, as described below and shown in FIG. 22, is mounted on
the inside of the cap 50 on a holder 214. A slider 216 having spring
electrical contacts 218 bridging the contacts on the circuit board 212 is
slidably supported by the holder. An operating knob 220 is rotatably
mounted on the outside of the cap 50 by means of a retainer ring 222 and
is coupled to a coupling disc 224 rotatably received in a round hole in
the cap 50, with a sealing ring 225 interposed, by an eccentric pin on the
disc 224 that is received in a slot on the underside of the knob 220 so
that rotation of the knob correspondingly rotates the disc. Another
eccentric pin on the other side (the inside) of the disc 224 runs in a
transverse guideway on the slider, so that rotation of the disc causes
translation of the slider so as to move the contacts to a selected one of
three positions along the printed circuit board 212. Detents act between
the slider and the holder to hold each switch position. Stop bosses on the
cap 50 are engaged by ribs on the underside of the knob 220 to restrict
rotation of the knob to that required to set the endmost two positions of
the slider relative to the printed circuit board.
The printed circuit board 212 and a diagram of the electrical circuit of
the drive unit 30 are shown in FIG. 22. The positive terminal of the
series--paired batteries 34, 36 is connected by a wire 230 to a first
conductor 232 of the circuit board and to one charger contact pin 60 by
the conductor 63. The negative battery terminal is connected to the
charger electrode pin 60 by the conductor 64 through a diode 234, which
prevents reversal of the current flow through the battery in case the
drive unit is plugged into an improper charger or forced, notwithstanding
provisions for preventing improper orientation, into its charger/holder in
a reversed position. The negative battery terminal is also connected by a
wire 236 to a second circuit board conductor 238. The terminals of the
motor 32 are connected by wires 240 and 242 to the respective circuit
board conductors 244 and 246. In the drawing the circles 248 and 250
represent the contact points of one of the two spring contacts 218 on the
slider 216, and the circles 252 and 254 represent the two contact points
of the other spring contact on the slider.
The contact points of the spring contacts are shown in FIG. 22 in the off
position of the switch assembly 210--the contact points 250 and 254 are in
contact with non-conductive zones of the circuit board 212, so no current
flows to the motor. Rotation of the knob 220 counterclockwise (with
respect to FIG. 22) slides the slider to the left and brings contact
points 250 and 254 onto the circuit board conductors 246 and 244,
respectively, thereby completing the following circuit path between the
battery terminals: battery positive, wire 230, conductor 232, spring
contact points 248 and 250, conductor 246, wire 242, motor 32, wire 240,
conductor 244, spring contact points 254 and 252, conductor 238, wire 236,
battery negative. Rotation of the switch knob clockwise from the "off"
position of the switch shown in FIG. 22 slides the slider 216 to the right
and completes the following circuit path between the battery terminals:
battery positive, wire 230, conductor 232, spring contact points 248, 250,
contact 244, wire 240, motor 32, wire 242, conductor 246, contact points
254 and 252, conductor 238, wire 236 and battery negative. In the left
position of the slider, the current flow through the motor 36 is reversed
from what it is when the slider is in the right position.
It will be recalled that when the crown gear 122 is rotated in one
direction, the cam surface of the cam insert 130 is concentric to the axis
of the crown gear and the brush head extension 140 remains stationary,
whereas when the crown gear is driven in the other direction, the cam
surface of the cam insert 130 is eccentric to the crown gear axis and
drives the brush head extension back and forth lengthwise. By selecting
one of the two "on" positions of the switch 210, the user can operate the
electric toothbrush in a mode in which the brush unit reciprocates
lengthwise relative to the drive unit such as to move the bristles from
side to side across the teeth or in a mode in which the brush unit remains
stationary relative to the drive unit. In both modes, however, the
bristles carried by each bristle holder pivot transversely, alternate ones
pivoting in a direction opposite to the others 180.degree. out of phase.
Preferably, though not essentially, the gear train for pivoting the
bristles laterally and the gear train for moving the brush unit lengthwise
are designed such that the frequency of lengthwise oscillation of the
brush unit is considerably less than the frequency of lateral pivoting of
the bristle holders; for example, a ratio of lengthwise frequency to
lateral frequency of about one-half or less is desirable. As discussed
above, such a relationship provides motions of the bristle tufts over the
teeth in sideways figure "8" patterns, which clean the teeth very
effectively and massage the gums in an especially advantageous manner,
involving fine-scale omnidirectional bristle motions. Desirable
frequencies for the brush motions are of the order of 1000 cycles per
minute for the lateral movements of the holders and of the order of 500
cycles per minute for the lengthwise movement of the brush head. The brush
head lengthwise stroke distance is preferably about 5.0 to 6.0 mm., and
the lateral excursions of the bristle tufts about 3.0 to 4.0 mm.
The provision of separate bristle holders facilitates the provision of
bristles of different stiffnesses or materials, if desired. The bristles
of the individual bristle holders of the group can be inserted in separate
tuft-inserting machines set up to run different bristles. For example, the
endmost two holders may have stiffer bristles than the remaining four, the
endmost two holders being fitted with bristles in a different machine from
that used for the other four holders (or the same machine set up for
separate runs of the different bristles).
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